CHEM 30. THERMODYNAMICS TEST QUESTIONS
FOR EXAM PREP 2024/2025
1 . Ethanol is often added to gasoline as a renewable component
that reduces harmful emissions. The mixture is known as gasohol.
In a research laboratory, the combustion of 3.50 g of ethanol in a
sophisticated calorimeter causes the temperature of 3.63 L of
water to increase from 19.88 o c to 26.18 o c. Use this evidence to
determine the molar enthalpy of combustion of ethanol.:
2. Write the symbols for the molar enthalpy of:
a) Combustion
b) Formation
c) Decomposition
d) Solubility
e) Fusion (melting)
f) Vaporization
g) Neutralization:
3. In your own words, describe the similarities and differences
between the enthalpy change and molar enthalpy symbols and
meanings.:
4. What is the significance of a positive or negative sign for
an enthalpy change or molar enthalpy value?:
5. Predict the enthalpy change for the combustion of every 100
g of methane in a natural gas water heater. éHm (CH4)= -802.5
kJ/moI (to produce water vapour):
1/12
, CHEM 30. THERMODYNAMICS TEST QUESTIONS
FOR EXAM PREP 2024/2025
6. Methanol is one type of fuel that is used in fondue heaters.
In an experiment using a simple tin can calorimeter, 2.98 g of
methanol was burnec temperature of 650 g of water by 20.9 o c.
Using this evidence, ca molar enthalpy of combustion of
methanol (to produce water as a vapour).:
7. Record whether each of these statements is true or false.
Provide your reasoning.
(a) Heat is possessed by a chemical system.
(b) For an exothermic change, energy exits from the
surroundings and enters the chemical system.
(c) The change in enthalpy of a chemical system is measured in
kilojoules per mole (kJ/moI).
(d) The change in thermal energy of the surroundings
can be calc Q -met.
(e) Temperature is the measure of the average kinetic energy of
the entities in a chemical system.:
8. Ethane is a component of natural gas. If the molar enthalpy of
combustion of ethane is -1.56 MJ/moI, calculate the quantity of
thermal energvnained h'/ the burning of
(a) 5.0 mol of ethane (b) 40.0 g of ethane:
9. Decane is one of the hundreds of compounds in gasoline.
The molar enthalpy of combustion of decane (CIOH22) is 6.78
MJ/moI. What ma would have to be burned in order to raise
the temperature of 500.C from 20.0 o c to 55.0 o c?:
10. During sunny days, chemicals can store solar energy in
homes for later release. Certain hydrated salts dissolve
endothermically in their water of hydration when heated to
decomposition heat when For example,
Glauber's salt, Na2S04•10 H20(s), solidifies at
32 o c, releasing 78.0 kJ/moI of salt. What is the enthalpy change
for the solidification of 1.00 kg of Glauber's salt used to supply
2/12
FOR EXAM PREP 2024/2025
1 . Ethanol is often added to gasoline as a renewable component
that reduces harmful emissions. The mixture is known as gasohol.
In a research laboratory, the combustion of 3.50 g of ethanol in a
sophisticated calorimeter causes the temperature of 3.63 L of
water to increase from 19.88 o c to 26.18 o c. Use this evidence to
determine the molar enthalpy of combustion of ethanol.:
2. Write the symbols for the molar enthalpy of:
a) Combustion
b) Formation
c) Decomposition
d) Solubility
e) Fusion (melting)
f) Vaporization
g) Neutralization:
3. In your own words, describe the similarities and differences
between the enthalpy change and molar enthalpy symbols and
meanings.:
4. What is the significance of a positive or negative sign for
an enthalpy change or molar enthalpy value?:
5. Predict the enthalpy change for the combustion of every 100
g of methane in a natural gas water heater. éHm (CH4)= -802.5
kJ/moI (to produce water vapour):
1/12
, CHEM 30. THERMODYNAMICS TEST QUESTIONS
FOR EXAM PREP 2024/2025
6. Methanol is one type of fuel that is used in fondue heaters.
In an experiment using a simple tin can calorimeter, 2.98 g of
methanol was burnec temperature of 650 g of water by 20.9 o c.
Using this evidence, ca molar enthalpy of combustion of
methanol (to produce water as a vapour).:
7. Record whether each of these statements is true or false.
Provide your reasoning.
(a) Heat is possessed by a chemical system.
(b) For an exothermic change, energy exits from the
surroundings and enters the chemical system.
(c) The change in enthalpy of a chemical system is measured in
kilojoules per mole (kJ/moI).
(d) The change in thermal energy of the surroundings
can be calc Q -met.
(e) Temperature is the measure of the average kinetic energy of
the entities in a chemical system.:
8. Ethane is a component of natural gas. If the molar enthalpy of
combustion of ethane is -1.56 MJ/moI, calculate the quantity of
thermal energvnained h'/ the burning of
(a) 5.0 mol of ethane (b) 40.0 g of ethane:
9. Decane is one of the hundreds of compounds in gasoline.
The molar enthalpy of combustion of decane (CIOH22) is 6.78
MJ/moI. What ma would have to be burned in order to raise
the temperature of 500.C from 20.0 o c to 55.0 o c?:
10. During sunny days, chemicals can store solar energy in
homes for later release. Certain hydrated salts dissolve
endothermically in their water of hydration when heated to
decomposition heat when For example,
Glauber's salt, Na2S04•10 H20(s), solidifies at
32 o c, releasing 78.0 kJ/moI of salt. What is the enthalpy change
for the solidification of 1.00 kg of Glauber's salt used to supply
2/12
